This invention generally relates to a line printer and more specifically to a mechanism for rotating a printing drum shaft or a paper advancement shaft in a line printer.
Various instruments and other data sources produce information for display as alphabetic, alpha-numeric or other characters by output devices, such as line printers. This invention is particularly applicable in a class of line printers comprising a printing drum in the form of a set of type wheels that rotate in unison on a common shaft intermittently between successive positions. A printing hammer is actuated whenever a comparison circuit indicates that a symbol or character on the type wheel then facing the material to be printed corresponds to the character actually to be printed by that wheel.
In prior printers of this type, such as shown in U.S. Pat. No. 3,731,622, assigned to the same assignee as the present invention, solenoid-actuated mechanisms advance the printing drum and a paper advance mechanism. The solenoid armature connects to a link through a pivot and the link rotates about a second pivot displaced from the first pivot. A pawl is also pivotally mounted on a third pivot on the link. A spring biases the pawl against a ratchet wheel. This mechanism tends to be rather bulky and, due to its several pivots, more difficult to manufacture.
Therefore, it is an object of this invention to provide a compact drive mechanism for rotating a shaft to successive discrete positions.
Another object of this invention is to provide a drive mechanism which is more reliable than prior mechanisms.
Still another object of this invention is to provide a drive mechanism which is of small size and relatively inexpensive to manufacture.